Link libfcgi against the math library.

Signed-off-by: Thomas Claveirole <thomas.claveirole@green-communications.fr>
[Louis: rebase on top of 2.4.2]
Signed-off-by: Louis Rannou <louis.rannou@smile.fr>

Index: b/libfcgi/Makefile.am
===================================================================
--- a/libfcgi/Makefile.am
+++ b/libfcgi/Makefile.am
@@ -18,4 +18,5 @@
                      os_@SYSTEM@.c
 libfcgi_la_CC      = @PTHREAD_CC@
 libfcgi_la_CFLAGS  = @PTHREAD_CFLAGS@
+libfcgi_la_LIBADD  = -lm
 libfcgi_la_LDFLAGS = @EXTRA_LIBS@ -no-undefined

 libfcgi___la_SOURCES = $(INCLUDE_FILES)       \
